FORMALIN is the best available fixative and is widely available from pharmacies worldwide. Full strength liquid formalin purchased in pharmacies is 37% formaldehyde dissolved in water. For adequate fixation in warm climates it is important to make a strong formalin solution. We recommend that for collections made in Congo a mix of ONE PART full strength formalin to FIVE parts clean water is used. While a "10%" formalin solution is usually recommended for fish fixation (this is made by combining 1 part full strength formalin with 9 parts clean water - the resultant dilution is actually only 3.7% to 4% formaldehyde) we find that this is not strong enough to properly fix specimens in Congo. Adequate initial fixation is critical for long-term preservation. Note that formalin is slightly acidic, and long term storage of fish in unbuffered formalin can result in bone deossification so it is best to add some marble chips, crushed oyster shell, or a few ml of borax to neutralize the formalin stock solution.